Downhole recovery production tube system

ABSTRACT

An improved oil well production tube system characterized by a series of seam-welded, coilable tubes configured for placement in a subterranean fluid recovery well. Smaller coilable tubes, contained within a larger coilable tube, are configured for providing power communication between the surface and a downhole recovery means. The larger coilable tube is configured for providing communication of a recovered fluid from downhole to the surface. During fabrication, one or more smaller coilable tubes is introduced along the surface of a length of flat strip metal. The smaller coilable tubes are preferably tack-welded to the surface of the flat strip metal at determined intervals along their length. The length of flat strip metal is formed into tubular form and seam welded to form a coilable tube containing the smaller tubes therein.

CITATION TO PRIOR APPLICATION

This application claims the benefit of U.S. Provisional Application No.60/651,873, filed on Feb. 8, 2005.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to an improved oil wellproduction tube system. More specifically, the present invention relatesto an oil well production tube system where one or more smaller coilablepower tubes is placed within a larger coilable production tube.

2. Background Information

The use of coilable production tubing for the transfer of fluid from asubterranean source to the surface is known in the art. However, suchproduction tubing systems heretofore devised and utilized are known toconsist basically of familiar, expected and obvious structuralconfigurations, notwithstanding the several designs encompassed by theprior art which have been developed for the fulfillment of manyobjectives and requirements. While these devices may fulfill theirrespective, particularly claimed objectives and requirements, theaforementioned devices do not disclose an improved oil well productiontube system such as Applicant's present invention.

Conventional artificial lift recovery systems employ a series of rigid,individual production tube segments joined to one another by threadingeach segment together. Typically, these segments are on the order ofthirty feet in length. Each individual link is connected to the next soas to form a final production tube extending between the surface andbottom of a well. Several problems are unavoidable with systemsemploying this type of production tubing. For example, a rigid,segmented production tube is prone to leaking recovered fluid about thepoint where individual segments are joined together. These problems areexaggerated when a well bore becomes warped or deviated; as such, manytimes rigid segments cannot be used in multiple well bores. Further,individual production tube segments are subject to cross-threading orother thread damage that may compromise the mechanical integrity of theproduction tube. When this occurs, heavy machinery (capable of producinghigh torque) must be used to unthread or separate individual segmentsfrom one another. Finally, in the event the production tubing must beremoved from the well bore, individual segments must be taken out of theground in linear fashion, extending several feet above the surface,before they can be completely removed from the well.

Commonly, artificial lift recovery systems employ electrical cables topower a downhole pump. However, these types of systems present severalproblems. For instance, electrical cable must be strapped to the outsideof each individual joint with bands or straps to hold the cable inplace. This involves the use of at least two additional personnel and aspooling unit. One person is needed to run the banding machine thatattaches the cable to the production tube and another person is neededto run the electrical cable spooling unit that contains the spool ofelectrical cable. Moreover, the cable itself must be sheathed in aprotective shield, or armor, to protect against abrasions that mightoccur during installation. Even when this protection is utilized, cabledamage can occur that causes an electrical short in the cable when poweris applied. The production tube and cable must then be pulled from thewell bore and repaired before it can be run back into the well bore.

It is not uncommon for the bands that hold electrical cable to break orbe installed improperly. When this occurs, since the armored electricalcable is not capable of supporting its own weight for the entire lengthof the production assembly, other straps break, ultimately resulting ina cable failure. In such an event, cable recovery from the well bore isan expensive and often unsuccessful process. Additionally, occasionallythe production tube disjoins and subsequently severs the electricalcable; of course, such a combination is especially difficult to retrievefrom the well bore.

Other practical difficulties are associated with the use of electricalcables in artificial lift recovery systems. Specifically, as a result ofgaps between the electrical cable and production tube, and theelectrical cable and protective armor, current blowout preventers cannot achieve a 100% positive seal. Moreover, in wells that have thepotential for heavy flowing, brine water must be constantly pumped inthe well bore while the pump is being installed. Also, the well boreinside diameter must be large enough to house both the production tubeand the electrical cable, which of course, limits the installing oflarge capacity pumps in smaller diameter well bores.

In view of the preceding, Applicant submits that hydraulically powereddownhole pumping systems are much more effective. Nevertheless,seemingly unavoidable problems are a major concern for those skilled inthe art. Use of a single coilable production tube provides no means forefficient hydraulic power communication between the surface and adownhole recovery device. Specifically, the use of coliable productiontube, alone, does not provide for efficient or reliable powercommunication between the surface and a downhole recovery device.Limitations of known coilable tube production systems are also groundedin their manufacturing process. Known coilable production tubemanufacturing processes do not lend themselves to placing smallercoilable, power tubes within a larger coilable production tube.Specifically, no fabrication process has been developed to allow forsuch a configuration. In the alternative, continuous power tube may be“guided” along the production tube from surface to downhole. However,this procedure is far from practical as binding, kinking, and slidingfriction make for an all to difficult task.

SUMMARY OF THE INVENTION

The general purpose of the present invention, which will be describedsubsequently in greater detail, is to provide an improved downholerecovery production tube system which has many of the advantages of suchsystems known in the art and many novel features that result in a newdownhole recovery production tube system which is not anticipated,rendered obvious, suggested, or even implied by any of the knownsystems, either alone or in any combination thereof.

In view of the preceding, Applicant's invention addresses problemsassociated with enabling power communication between the surface and adownhole recovery means of an oil or gas recovery system. The inventionemploys use of one or more coilable power tubes placed within a largercoilable production tube. For example, two smaller coiled tubing tubesmay be placed inside the larger coiled production tube, such as two ¾″tubes inside a 2″ coiled production tube.

Use of the present system would offer several advantages over currentsystems. For instance, conventional, double-derrick, work-over rigscurrently utilized to remove and install jointed tubing strings from thewell bore would no longer be necessary in production operations. Theproposed hydraulically operated pumping systems utilize a mast mountedcoiled tubing unit to install the pumping components. Pump installationtime is reduced by at least 50%, simply due to not having to screwtogether several joints of conventional production tubing. The coiledtubing unit has a spool containing the coiled production tube with thetwo coiled tubing power strings already installed inside. Pumpinstallation involves the following steps:

-   -   1. Move in and rig up a mast mounted coiled tubing unit. Install        blowout preventer utilizing hoist mounted on the coiled tubing        mast.    -   2. Pick up pump and secure it in the top of the well bore        utilizing the same hoist.    -   3. Connect production coiled tubing and internal, coiled,        hydraulic lines to the downhole pump.    -   4. Purge hydraulic lines of all air. Test connection where        production tubing is installed.    -   5. Lower pump and production assembly into the well bore to the        desired depth.    -   6. Land production coiled tubing in surface well head.    -   7. Remove the blowout preventer.    -   8. Install power lines to hydraulic pump and production lines to        production tubing.

Because the power strings are inside the production tubing, blowoutpreventers have the “slick” outside surface of the production tubing toobtain a 100% seal. In the instance the production tube should separate,the smaller inner diameter power strings remain protected inside theproduction tube, making the production tube much easier to retrieve fromthe well bore. The two power strings are effectively shielded from anyabrasion that might occur during installation operations. Because thereis no outside power cable, smaller diameter well bores will be able torun larger pumping systems.

As will be discussed, the preferred form of the present inventionincorporates use of coilable tubing made from flat stock metal whereadjoining ends of stock metal segments, cut at supplementary angles, areconsecutively joined. The attributes associated with such process allowfabrication of a tubing string of up to 20,000 feet in length or more ina single pass operation. This process, preferably used to fabricatecoilable tubing of the present system, is described in U.S. Pat. No.4,863,091; and the coilable tubing preferably used in the present systemis described in U.S. Pat. No. 5,191,911. Each are hereby expresslyincorporated by reference.

The coiled tubing and associated fabrication process described in theabove-referenced documents teach a continuous coilable tube formed byjoining consecutive lengths of stock metal. Stock metal lengths arejoined together at supplemental angles, preferably of 30 degrees, andwelded together with the aid of “wings” acting as heat sinks. Theadjoining weld is machined and then sent through a normalizing heattreatment process. Finally, the joined lengths are formed and welded inlongitudinal fashion to form a continuous tube. Extraordinary strengthand flexibility of the tube is provided by the helical weld about themetal stock lengths.

Unlike what is known in the art, the present system employs use ofadjacent fabrication systems whereby one or more smaller tubes areformed. These smaller tubes undergo welding, machining, andnormalization procedures as known in the art. However, unlike thattaught in the prior art, the smaller tubes are adjacently placedlengthwise along a strip of joined stock metal having a relatively largewidth (thereby providing for a tube of larger circumference).Preferably, the smaller tubes are introduced to an assembly line withthe large stock metal strip after the welded joints between large stripsegments has gone through the normalization process. As such, thesmaller tubes may rest along the larger stock metal strip lengths whereone or more smaller tubes, in combination with the large stock metal,enter a tube former as known in the art. When the strip stock, havingthe smaller tubes resting thereon, reaches the tube former, it is shapedinto tubular form with a seam running along its length. This seam iswelded and the resulting tube is then sent on to further processing,such as heat or electrochemical treatment.

Importantly, the smaller power tubes must be spaced with respect to oneanother along the large stock metal surface so that as the large tube isformed with the smaller tubes contained therein, the smaller tubesremain appropriately aligned with respect to one another. Correctspacing of the smaller tubes can be determined given the circumferenceof each smaller tube, and the circumference of the larger tube. Morespecifically, the smaller tubes should not be pressed against oneanother so as to compress or deform the smaller tubes. Preferably, eachsmaller tube is welded to the large stock metal strip surface ininterval fashion. This weld may be a simple tack-weld and is meant toensure the smaller tubes do not bind or “wrap around” the interior ofthe larger production tube during coiling and uncoiling. Perhaps mostimportantly, however, securing the smaller tubes along the interior ofthe larger tube eliminates unstabilizing movement of the power tubescreated in response to forces created by hydraulic fluid circulatingthere-through.

The novel attributes of the present system are apparent in bothmanufacture and operation of the present system. The method ofmanufacture associated with the present system provides for fabricationof an extraordinarily long, continuous series of coilable tubes in asingle pass. This feature, not available with known systems, providesfor savings in terms of both cost and time. A number of smaller tubesmay be independently introduced and arranged upon the larger strip metalsurface. The larger strip surface is then formed into a larger tubeirrespective of the number of tubes contained therein. As a result, alarger coilable tube, containing a plurality of smaller coilable tubes,is formed a single pass procedure. This is particularly important as theproduction time of a tube containing many smaller tubes is exactly thatof a tube containing one smaller tube.

During operation, the smaller coilable tubes house power communicationmeans, either electrical or hydraulic, that extend between the surfaceand a downhole recovery unit. For example, arrangement of the smallertubes within a larger tube provides an excellent mechanism for thetransfer of hydraulic power fluid, which is thought to be mostbeneficially used where a submersible, hydraulically actuated, recoverymeans is placed downhole. The system also makes it possible to safelyextend electrical power lines between the surface and an electricallydriven recovery means without being exposed to harmful agents.

Unlike systems known in the art, the present invention provides a systemwhereby electrical power lines can extend between surface and downholein a safe, sealed environment. Where known systems employ a single tubeextending between surface and downhole, electrical power lines extend inexposed fashion along the interior or exterior of the production tube.In either case, the power lines remain in a precarious situation as theyare exposed to corrosive materials, possible abrasions, and are subjectto being damaged by warping deviation of the well bore. However, thepresent system allows electrical power lines to remain protected insmall coiled tubes along the interior of the production tube.

BRIEF DESCRIPTION OF THE DRAWINGS

Applicant's invention may be further understood from a description ofthe accompanying drawings, wherein unless otherwise specified, likereferenced numerals are intended to depict like components in thevarious views.

FIG. 1 is a perspective view of a known system for producing seamlesscoilable tubing.

FIG. 2 is a perspective view of the preferred embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, a prior art system of producing a tubing stringfrom flat sheet metal strips is shown. Such is disclosed in U.S. Pat.No. 4,863,091 and U.S. Pat. No. 5,191,911, each of which is herebyexpressly incorporated by reference. In this system, the apparatusincludes master coils 50 and 52, an accumulator 56, a feed stockconditioner 58, a tube former 60, a heat treater 64, and a reel 66. Asknown in the art, stock metal is deployed from master coils 50 and 52and is “run through” accumulator 56. Differential action on the part ofaccumulator 56 allows a second length of strip stock to be spliced ontothe trailing end of a preceding length while the latter is still housedin accumulator 56. Splice 68 is formed by cutting strip ends to bespliced at supplementary angles, including an acute angle of aboutthirty degrees. A small piece 70 is attached to each end of splice joint68 to act as a heat sink and provide for improved weld strength. Awelding tool is passed along the splice 68. After splice joint 68 hasbeen welded the joint is machined or finished to remove excess weldment,this is typically done with grinders applied to each surface of thejoined strips. After grinding, the weld is normalized be somenormalizing means. Normalizing means preferably is a resistance heateras known in the art. Application of normalizing means varies accordingto desired application of the produced tubing string. The strip stockthen reaches tuber former 60 and is shaped into tubular form with a seamrunning along its length. The welded tubing then passes immediately toheat treater 64. Finally, from the heat treater 64 the tubing is reeledonto storage reel 66.

Referring to FIG. 2, the system of the present invention is depicted.One or more apparatuses are shown for producing coilable tubing.Importantly, several apparatuses may be arranged with respect to theother so that a single, larger coilable tube may be produced containinga different number of smaller tubes therein with no reconfiguration ofany apparatus. As mentioned, concurrent and independent operation ofeach apparatus provides for a time and costs saving not yet achieved inthe art. As shown, any number of smaller coilable tubes, generallydesignated by the reference numeral 100, is introduced to the surface ofjoined strip metal 102. In the preferred embodiment, each tube 100 isintroduced to joint metal strip 102 after strip 102 has passed throughstock conditioner 58 but before strip 102 enters tube former 60.

Preferably, each tube 100 is intermittently welded to the surface ofstrip 102 so that each remains longitudinally fixed with respect tostrip 102. Each weld is then machined, by grinder or the like, so as toform an even seam between each tube. This, of course, promotes even flowor production fluid and efficient operation. Each tube 100 is spacedfrom the other so that as strip 102 is formed into a tube by tube former60, each tube 100 is not unduly pressed against the other. Such anarrangement, however, does provide for each tube 100 to be arranged inadjacent fashion within the larger coiled tube. As mentioned, weldingeach tube 100 to the surface of strip 102 provides for several benefits,including efficient operation and the prevention of bending or kinkingof component tubes.

The physical configuration of the present apparatus lends itself to anovel process of installing, or initiating operation of an artificiallift recovery system. This process, in conjunction with production tubedescribed herein, provides for tremendous savings with regard to timeand money. Accordingly, a downhole recovery pump installation would usethe following steps:

-   -   1. Move in and rig up mast mounted coiled tubing unit. Install        blowout preventer utilizing hoist mounted on the coiled tubing        mast.    -   2. Pick up pump and secure in the top of well bore utilizing the        same hoist.    -   3. Connect production coiled tubing and internal, coiled,        hydraulic lines to the downhole pump.    -   4. Purge hydraulic lines of all air. Test connection where        production tubing is installed.    -   5. Lower pump and production assembly into the well bore to        desired depth.    -   6. Land production coiled tubing in surface wellhead.    -   7. Remove blowout preventer.    -   8. Install power lines to hydraulic pump and production lines to        production tubing.

Although the present invention has been described with reference tospecific embodiments, this description is not meant to be construed in alimited sense. Various modifications of the disclosed embodiments, aswell as alternative embodiments of the inventions will become apparentto persons skilled in the art upon the reference to the description ofthe invention. It is, therefore, contemplated that the appended claimswill cover such modifications that fall within the scope of theinvention.

1. A coiled tubing system, comprising: a first continuous length ofcoiled tubing; and a second continuous length of coiled tubing, saidfirst continuous length of coiled tubing having a larger diameter thansaid second continuous length of coiled tubing, said second continuouslength of coiled tubing being embedded within the inner diameter of saidfirst continuous length of coiled tubing.
 2. The system of claim 1wherein said second continuous length of coiled tubing is attached tothe inner wall of said first continuous length of coiled tubing.
 3. Thesystem of claim 1 further comprising a third continuous length of coiledtubing juxtaposed along said second continuous length of coiled tubingembedded within said first continuous length of coiled tubing.
 4. Thesystem of claim 3 wherein said second and third continuous lengths ofcoiled tubing are attached to the inner wall of said first continuouslength of coiled tubing.
 5. A method of manufacturing a coiled tubingsystem comprising the steps of: introducing a first continuous length ofcoiled tubing onto a surface a continuous length of flat metal;arranging said first continuous length of coiled tubing onto saidsurface of said continuous length of flat metal such that thelongitudinal axis of said first continuous length of coiled tubing isparallel to the sides of said continuous length of flat metal; fixingsaid first continuous length of coiled tubing along the length of saidsurface of said continuous length of flat metal; and forming saidcontinuous length of flat metal into a second continuous length ofcoiled tubing wherein said first continuous length of coiled tubing isfixedly contained within said second continuous length of coiled tubing.6. A method of manufacturing a coiled tubing system comprising the stepsof: introducing a first and second continuous length of coiled tubingonto a surface of a continuous length of flat metal; arranging saidfirst and second continuous lengths of coiled tubing onto said surfaceof said continuous length of flat metal such that the longitudinal axisof said first and second continuous lengths of coiled tubing areparallel to the sides of said continuous length of flat metal; fixingsaid first and second continuous lengths of coiled tubing along thelength of said surface of said continuous length of flat metal; andforming said continuous length of flat metal into a third continuouslength of coiled tubing wherein said first and second continuous lengthsof coiled tubing are fixedly contained within said third continuouslength of coiled tubing.